README.md: Add guide, tidy

README.md: Update spec version, tidy links

README.md: Reconcile spec versions, minor edits

README.md: Update resources

set textwidth=0

README.md: Rewrite "Install" section

README.md: New screenshot

README.md: Give vim packages example

README.md: Rewrite 'Install' section

README.md: Rewrite installation

README.md: Add screenshot, installation, resources

Set 'wrap' option

Remove .gitignore

Rename to gemini.vim

Add LICENSE

Inital syntax and ftdetect files

Initial commit